The long term goals of this study are to characterize extracellular and cell associated factors which either play a role in the disease process or induce a protective host response against the group B streptococci. Particular emphasis in this study is to examine the role of extracellular neuraminidase, proteases, and protection-inducing type specific antigen that is released by the various serotypes of group B streptococci. Serotype III isolates from infected infants can be divided into two major physiological categories based on the elaboration of these extracellular enzymes and antigens. Strains producing high levels are more often isolated from infected infants. Studies are in progress to purify and characterize these extracellular products and to examine their virulence in a mouse model. It is anticipated that antisera raised against these factors will allow an examination of their role in virulence by challenging mice with the virulent organism in combination with antiserum to the specific factor under study. These studies can then be extended to an examination of the level of antibody to these products in the mother and neonate to determine what antibodies and the level of antibodies which correlate with protection in the neonate.